Transmission mechanisms which are movable relative to a power shaft to increase and decrease the radius of an arcuate power stroke delivered to a driven member are typified by the structures disclosed in U.S. Pat. Nos. 4,129,044 to Erickson et al and 4,164,153 to Moritsch et al. Typical gear change mechanisms which utilize rotationally associated inner and outer drive and driven members can be seen in the just noted patent to Moritsch et al and in U.S. Pat. No. 3,081,641 to Iseman.
A number of devices which include a chain wheel and a pedal crank shaft having toothed ratchet mechanisms interposed therebetween are disclosed in those patents classified in Class 180, subclasses 230, 231; Class 280, subclasses 236, 238, 251, 259, 260, 261, 262 and 431; Class 284, subclasses 431 and Class 474, subclasses 55, 69 and 70 and Class 74, subclasses 190, 190.5, 194, 393 and 810.
Automatic variation in the gear pitch and thus the power arc of a transmission; and in the transmission ratio between a transmission and its driven element, as partially achieved in transmissions of the type typified in the above-mentioned Moritsch et al construction, present problems not heretofore resolved, including the achievement of smooth unmeshing of driving and driven members after passing through the power arc of rotation, the provision of automatic changes in the gear pitch, and thus in the ratio of transmission, through the full range capacity of the transmission, and of optional modes of manual and automatic operations.
Furthermore, transmissions of the infinitely variable type of the prior art tend to be complicated and include a large number of parts for their operation.